Serpentine spring



aim

C. V. WOLFE +k. Mm

SERPENTINE SPRING Filed March 29, 1946 Au 1, 195m INVENTOR. Char/es ZZ VVb/fe, BY:

ATTORNEY Patented Aug. 1, 1950 UNITED SERPENTINE SPRING Charles V. lNolfe, Kndianapolis, Ind, assignor to E. C. Atkins and Company, Indianapolis, Ind.,

a corporation of Indiana Appiication March 29, 1946, Serial No. 658,166

1 Claim. 1

The present invention relates to a serpentine spring, and the primary object of the invention is to produce such a spring which, when supported against distortion out of its plane of intended expansive and contractible movement, will respond with high uniformity to forces exerted against it in that plane, and will be stronger than previously-know serpentine springs produced from stock of corresponding size. A further object of the invention is to improve the action, strength, and life of serpentine springs.

To the accomplishment of the above and related objects, my invention may be embodied in the form illustrated in the accompanying drawings, attention being called to the fact, however, that the drawings are illustrative only, and that change may be made in the specific construetion illustrated and described, so long as the scope of the appended claim is not violated.

l is a plan view of a serpentine spring constructed in accordance with my invention and mounted in a suitable supporting guide;

Fig. 2 is an enlarged fragmental perspective view of a spring constructed in accordance with my invention; and

Fig. 3 is a transverse section taken substantially on the line 3--3 of Fig. 2.

Serpentine springs are ordinarily formed by merely bending wire or bar stock of any suitable uniform cross-sectional contour, into serpentine U shape comprising a series of alternately reversely placed portions of generally U-shape. Such springs, so formed, are quite unreliable because of the unavoidable lack of uniformity of resistance of the curved portions of the U bases to forces applied in the direction of length of the spring. This variability of resistance is due, of course, to the varying relation of the axis of the spring stock to the line of application of force, as the stock progresses around the curve. Thus the leverage effect of such force, applied to incrementally successive portions of the spring stock varies unavoidably. This condition makes for lack of reliability in service, and frequently results in rupture of springs so formed.

I have found that the above-mentioned weakness and unreliability can be overcome by varying the transverse dimension of the spring stock, in the plane of expansive and contractible movement of the spring, to produce maximum spring stiffness at the bases of the U sections, and minimum stiffness at the median portions of the arms of the U sections. Ideally, such transverse dimension is increased gradually and substantially uniformly from the mid point of each arm to the middle of each adjacent U base, though some of the advantages of my invention can be attained even if the transition from a minimum dimension to a maximum is sudden.

According to my present belief, my invention can best be practiced by first forming a serpentine from temperable rod of uniform (preferably round) cross-section. Now pressure is applied to the U sections on either side of the median plane of the serpentine, preferably at slight (and opposite) angles converging toward said median plane, to produce the sloping surfaces I0 and II on the upper surfaces of each U and the corresponding sloping surfaces I2 and 13 on the lower surfaces thereof. Thereby, the metal of the stock is caused to flow outwardly in the plane of the serpentine to increase the lateral width of the stock gradually from a minimum at the midpoints M of the arms 15 thereof to a maximum at the midpoints 16 of the bases thereof.

Any variation in the lateral dimension of the stock from which the serpentine is formed, whereby that lateral dimension is greater in the bases of the U sections than in the arms thereof, will improve the action, reliability and life of a serpentine spring; and I do not wish to be limited to specific variations. However, for purposes of illustration, it may be said that I now consider opitimum conditions to be indicated by the following example: If the rod is initially 0.150" in diameter, uniform distortions throughout the length of the spring under lengthwise compression will occur if the thickness at the points It is reduced, in the manner described, to 0.075 while the thickness at the points 14 remains 0.150.

I claim as my invention:

A serpentine spring comprising a series of successively reversely positioned U sections, the transverse dimension of each such section, .in the median plane common to the bases and legs of all such sections, being a maximum at the midpoint of its base and diminishing gradually to a minimum at the midpoints of its arms.

CHARLES V. WOLFE.

REFERENCES CITED The following references are of record in the file of this patent:

' UNITED STATES PATENTS Number Name Date 345,767 Buckley July 20, 1886 1,893,098 Murray Jan. 3, 1933 2,202,301 Probst May 28, 1940 

